This invention relates in general to a construction of respirator devices and in particular to a new and useful humidity exchanger for a breathing device.
In breathing devices it must be ensured that the air passages of the patients do not dry out and that his heat balance is not disturbed. The risk exists particularly when the cold inhaled air is supplied to the patient through a tracheotomy tubule or through an intratracheal catheter. In these cases the rhinopharingeal area, where the inhaled air is normally humidified and heated, is bypassed.
In order to prevent drying and cooling, it is known to provide ventilating air humidifiers to bring the inhaled air to a volume of more than 70% relative humidity, and approximately to body temperature.
Subdivided according to the principal design, ventilating air humidifiers are known with humidification of the ventilating air from a water supply and by a humidity exchange from the humid exhaled air into the relatively dry inhaled air.
In a ventilating air humidifier from a water supply, the supply of the ventilating air is effected from an air supply to the patient through a corrugated hose, inside this hose is arranged a folded water-carrying hose which is connected with its connection to the water supply. The wall of the water hose is waterproof, but is permeable to water vapor. The ventilating air conducted through the corrugated hose surrounds the water-carrying hose. It is humidified by the water passing through in vapor form. In a further development, the ventilating gas-carrying hose can be arranged in a water bag hanging around the neck of the user connected into the ventilating gas connection to the breathing apparatus or directly from the surrounding atmosphere to the user. The breathing hose with polytetrafluorethylene walls, extending in ascending and descending turns, can be a part of the water bag. Its inlet can be connected either directly to the atmosphere or to a portable container with liquid oxygen. Its outlet leads to a tracheotomy tubule or to a nose catheter. It is indicated that the water supply is heated by the body heat.
A disadvantage is the relatively large water supply which is necessary and whose temperature must be controlled and whose large volume close to the patient is always a potential risk when the water supply runs out. Adequate humidification of the ventilating air of the ventilating gas requires larger diameters for the ventilating air guide. These known ventilating air humidifiers are therefore very large. Heating the inhaled air by the body temperature over the water supply is also very problematic (U.S. Pat. No. 3,871,373).
Another known ventilating air humidifier for respiration with humidification from a water supply also contains a waterproof foil which is permeable, however, to water vapor and which is charged on one side with warm water, while the ventilating gas to be humidified passes by the other side charged with gas.
The evaporation surface is made in star form to achieve a greater evaporative power. In order to further reduce the size of the ventilating air humidifier without reducing the evaporation surface and thus the evaporative power, the water vapor-permeable foil was formed in an additional patent by the walls of hollow fibers. The hollow fibers are arranged as a bundle parallel to each other in a housing. They are secured together with a water feed and a water discharge pipe on the end faces of a packing. The water to be evaporated is fed and discharged through the water carrying pipes. It wets the hollow fibers.
This type of ventilating air humidifier also depends directly on a relatively large water supply. The heating requires special measures (German Pat. No. 24 30 875 with additional U.S. Pat. No. 2,617,985).
In a known humidity exchanger in apparatus for ventilation and anesthesia, in which the humidity contained in the ventilating air is separated, and the separated water is evaporated into the inhaled air, the respiration and expiration channels extending in counter-flow have a diffusion foil as a common partition so that the water contained in the exhaled air in vapor form can get by diffusion through the diffusion foil into the inhaled air. In order to prevent the heat contained in the exhaled air from escaping into the surrounding atmosphere, the humidity exchanger can be surrounded by a heat insulation. Humidity exchangers of this type are very large. An adequate passage of water vapor requires a corresponding large foil surface in long expiration and inspiration air channels. The heat insulation must insulate these channels well from the atmosphere so that the inhaled air is sufficiently heated. (DOS No. 25 29 050).